JPH0468267A - Cryogenic refrigerating machine - Google Patents

Abstract

PURPOSE:To shorten the cooling down time period and maintain the refrigerating capacity by a method wherein a cylinder assembly and a valve motor assembly are connected by two refrigerant pipes having different diameters and the two refrigerant pipes are alternatively changed over to each other depending upon the operating status. CONSTITUTION:In an expansion device 2, the high pressure gas supplied from a compressor 1 is adiabatically expanded to generate cold of a cryogenic level. The expansion device 2 is separated into two assemblies, a cylinder assembly 3 where gas is expanded in expansion chambers 18 and 19 in a cylinder 10, and a valve motor assembly 40. The cylinder assembly 3 and the valve motor assembly 40 communicate with each other by a first refrigerant pipe 60 and a second refrigerant pipe 61 having a smaller diameter. During cool-down operation, the cylinder assembly 3 and the valve motor assembly 40 communicate with each other by the second refrigerant pipe 61 having a smaller diameter. With an increase in the flow rate or refrigerant flowing in and out, the compression heat which is taken away at the low temperature end of the cylinder 10 is dissipated well by heat-exchanging with the refrigerant gas. When normal operating state is established, the first refrigerant pipe 60 having a larger diameter is opened so as to increase the operating capacity of a refrigerating machine.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention reciprocates a displacer within the cylinder of an expander using gas pressure, and by adiabatic expansion of refrigerant gas accompanying the reciprocating movement of the displacer, the refrigerant gas can be heated to a cryogenic level. It relates to a cryogenic refrigerator that generates cold.

(Prior Art) Conventionally, as this type of cryogenic refrigerator, a gas pressure-driven GM refrigerator having a refrigerant cycle of a GM (Gifford ψ McMahon) cycle has been known. The expander of this refrigerator includes a cylinder, a displacer and a slack piston that are reciprocally disposed within the cylinder, and an expansion chamber is defined at the tip of the cylinder by the displacer. It communicates with the space on the base end side of the cylinder via the inner flow generator.

The slack piston is arranged on the proximal end side of the cylinder so as to partition the proximal space into a gas supply/discharge chamber and an intermediate pressure chamber,
The displacer is engaged with the displacer so as to drive the displacer with a delay of a predetermined stroke. While the intermediate pressure chamber is communicated with the surge volume,
The gas supply/discharge chamber communicates via a switching valve with a high pressure gas inlet and a low pressure gas outlet connected to the discharge side and suction side of the compressor, respectively. Then, by driving the switching valve with a valve motor, the supply and discharge of refrigerant gas to and from the gas supply and discharge chamber or the expansion chamber is switched, and the slack piston is moved by the differential pressure between the gas supply and discharge chamber and the intermediate pressure chamber, thereby displacing the displacer. The displacer is moved back and forth, and the refrigerant gas expands in the expansion chamber as the displacer moves back and forth, thereby generating cold in the cylinder around the expansion chamber.

Incidentally, in recent years, superconducting quantum interference devices (Super
conductive Quantum Interf
erence Device 2 (abbreviated as 5QUID) is attracting attention. By connecting a magnetic flux input circuit consisting of a superconducting coil to this 5QUID, a gradiometer can be obtained that can measure extremely weak magnetic flux, such as the magnetic field associated with a minute current flowing inside a living body or the magnetic field from a minute magnet inside the body. be able to.

However, when using the gas pressure-driven GM refrigerator described above to cool the 5QUID to the operating temperature level, the refrigerator is equipped with a valve motor to drive the switching valve; The magnetic flux from is 5QU
There is a problem in that the noise is detected as harmful noise to the ID, and its measurement accuracy is reduced.

Conventionally, in order to reduce the influence of the valve motor, the valve and valve motor in the expander are separated from the cylinder part, and the separated valve motor assembly and cylinder assembly are connected with refrigerant piping to reduce the valve motor. 5QUID, that is, a separate type that is placed away from the cylinder tip to reduce harmful noise caused by magnetic flux from the valve motor, has been proposed (for example, 198B, 5th Conference held from 8.18 to 8.19). International Cryoc
U.S. paper “Development of A Hybrid
Gulfford-Memahon J6ule-Th
ospson Ba5ed Neurowagne
toIIeter, Cryosquid”).

(Problem to be Solved by the Invention) However, in such a separate type expander, compared to an integrated type in which the valve motor is integrated with the cylinder part, the circulation between the compressor and the expander is reduced. Since the amount of refrigerant gas is reduced, the compression heat taken by the gas at the low-temperature end (tip) of the cylinder is not sufficiently radiated and accumulates in the room-temperature part (base end) of the cylinder. This retention of heat heats the surge volume located at the base end of the cylinder, increasing the internal gas pressure and reducing the differential pressure between the intermediate and high gas pressures, allowing the slack piston and displacer to move smoothly. This poses problems such as hindering movement, prolonging the cool-down time, and in the worst case, causing the displacer to stop.

This problem can be solved to some extent by using a small diameter refrigerant pipe. In other words, when the refrigerant piping is small in diameter, the amount of refrigerant gas flowing back and forth between the cylinder assembly and the valve assembly is larger than in the case of a large-diameter refrigerant piping, which promotes the radiation of compression heat and transfers heat to the room-temperature end of the cylinder. This is because it becomes difficult to accumulate.

However, on the other hand, if the refrigerant piping has a small diameter, the pressure loss of the gas at that part will increase, the so-called PV indicated area determined by the pressure and volume of the refrigerant gas will become smaller, and the refrigerating capacity will inevitably decrease.

For example, Figures 5 to 7 show the results of experiments conducted by the present inventors. A Pv diagram is shown with a refrigerant pipe connected by a refrigerant pipe with a diameter of 3/8'.

This figure shows that in the separate expander, the movement of the displacer is obstructed, and the refrigerating capacity of the refrigerator is reduced. Figure 6 shows the relationship between the diameter and length of the refrigerant piping and the Pv surface ratio, and Figure 7 shows the relationship between the diameter and length of the refrigerant piping and the temperature at the normal temperature end (head) of the cylinder. are shown respectively, and the longer the piping length, the
It can also be seen that the smaller the pipe diameter, the lower the temperature at the cylinder normal temperature end, but on the other hand, the 27 area ratio becomes smaller.

The present invention has been made in view of the above, and its purpose is to eliminate the influence of heating on the surge volume and stabilize the reciprocating motion of the displacer by making certain improvements to the above-mentioned separate expander. The aim is to maintain a shortened cool-down time while at the same time reducing pressure loss in the connecting piping to ensure refrigerating capacity.

(Means for Solving the Problems) In order to achieve the above object, in the invention of claim (1), in a separate expander, the cylinder assembly and the valve motor assembly are connected to two parallel refrigerants having different diameters. The two refrigerant pipes are connected by piping, and the two refrigerant pipes are switched depending on the operating state of the refrigerator.

Specifically, as shown in FIG. 1, this invention includes a compressor (1) that compresses refrigerant gas to generate high-pressure gas, and adiabatic expansion of the high-pressure gas supplied from the compressor (1). In the cryogenic refrigerator, the expander (2) is inserted into the cylinder (10) through the gas supply/discharge port (5). A cylinder assembly (3) that supplies and discharges gas to reciprocate the displacer (16) and expand the gas in expansion chambers (18) and (19) in the cylinder (10), and a valve motor (5).
4) drives the switching valve (51) to connect the high pressure gas port (43), low pressure gas outlet (44) and gas supply/discharge port (45) connected to the discharge side and suction side of the compressor (1), respectively. ) and a valve motor assembly (40) that switches communication with the valve motor assembly (40).

The gas supply/discharge port (5) of the cylinder assembly (3) and the gas supply/discharge port (45) of the valve motor assembly (40) are connected to the first refrigerant pipe (60) and the first refrigerant pipe (60). The first refrigerant pipe (60) is connected in parallel with the second refrigerant pipe (61) and communicates with the second refrigerant pipe (61) having a smaller diameter than the first refrigerant pipe (60).

Further, switching means (62), (63) are provided for selectively switching the communication between the gas supply/discharge ports (5), (45) to the first or second refrigerant pipes (60), (61).

In the invention of claim (2), in the same configuration as the invention of claim (1), as shown in FIG. The gas supply/discharge port (45) is connected with a plurality of refrigerant pipes (65) and (66).

In addition, by changing the number of refrigerant pipes (65), (66) that communicate between both gas supply and discharge ports (5), (45), it is possible to a large cross-sectional area mode in which at least two or more refrigerant pipes (65) and (66) are selected, and a refrigerant pipe whose cross-sectional area is smaller than the passage cross-sectional area in the large cross-sectional area mode. A switching means (6) for switching between the small cross-sectional area mode and the
7).

(Function) With the above configuration, in the invention of claim (1), for example, during cool-down operation of the refrigerator, the switching means (62),
(63) each gas supply/discharge port (5) of the cylinder assembly (3) and valve motor assembly (40),
(45) are communicated through a small-diameter second refrigerant pipe (61). During cool-down operation of the refrigerator, the cylinder (10
) is high at the low-temperature end, the influence of compression heat retention at the room-temperature end is greater than after cool-down.
By communicating through the refrigerant pipe (61), the amount of refrigerant gas flowing back and forth through this small-diameter refrigerant pipe (61) increases, and the heat of compression taken away at the low temperature end of the cylinder (lO) is exchanged with the refrigerant gas. This allows for better heat dissipation.

Therefore, the temperature rise at the normal temperature end of the cylinder (10) can be effectively suppressed and the intermediate pressure can be maintained within an appropriate range, so that the reciprocating motion of the displacer (16) can be maintained normally.

On the other hand, when the cool-down operation of the refrigerator is completed and the normal operating state is reached, the switching means (62) and (63) switch the gas supply and discharge ports (5) of the cylinder assembly (3) and the valve motor assembly (40).

(45) may be communicated through the large-diameter first refrigerant pipe (60). This large-diameter refrigerant pipe (60) reduces gas pressure loss and maintains a large Pv area, thereby increasing the refrigerating capacity of the refrigerator.

In the invention of claim (a), during cool-down operation of the refrigerator,
The gas supply/discharge port (5) of the cylinder assembly (3) and valve motor assembly (40) is controlled by the switching means (67).
), (45) are communicated with each other in a small cross-sectional area mode (for example, through a small number of refrigerant pipes (66)). For this reason, both gas supply and discharge ports (5).

(45) The cross-sectional area of the passage that communicates with each other becomes smaller, and the amount of refrigerant gas flowing back and forth between both gas supply and discharge ports (5) and (45) on the same dirt floor increases.
0) It is possible to effectively suppress the temperature rise at the room temperature end and maintain normal reciprocating motion of the displacer (16).

On the other hand, after the cool-down operation, the gas supply and exhaust port (5)
, (45) in a large cross-sectional area mode (for example, through a large number of refrigerant pipes (65) and (66)), the cross-sectional area of the communication passage increases as a whole, and therefore, Gas pressure loss in the refrigerant pipes (65) and (66) can be reduced to increase the refrigerating capacity of the refrigerator.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows a gas pressure driven GM according to a first embodiment of the present invention.
The pattern shows the overall configuration of a low-temperature refrigerator. This refrigerator is used as a pre-cooling refrigerator for a JT refrigerator (not shown) that utilizes Joule-Thomson expansion of helium gas (refrigerant gas). ) to cryogenic levels.

In the figure, (1) is a compressor that compresses helium gas to generate high-pressure gas, and (2) is a compressor that adiabatically expands the high-pressure gas supplied from compressor (1) to generate cryogenic cold. This expander (2) includes a cylinder assembly (3) and a valve motor assembly (
40).

The cylinder assembly (3) includes a bottomed cylindrical cylinder (10) that is open upward, and a valve stem (4) that airtightly closes the opening on the upper end side (base end side) of the cylinder (10). has. The valve stem (4) has a cylindrical protrusion (4a) that protrudes concentrically within the cylinder (10) at a predetermined distance from the inner wall thereof. The valve stem (4) also has a gas supply/discharge port (5) that opens on the cylinder centerline on its top surface, a relatively small surge volume (7), and a gas supply/discharge port (5) that opens on the cylinder centerline. (
10), and a gas flow path (8) communicating therewith is formed. Further, the gas flow path (8) is always in communication with the surge volume (7) via a communication path (9) with a small passage cross-sectional area, and this communication path (9) allows the surge volume (7) to The intermediate pressure is set to an appropriate value.

On the other hand, the cylinder (10) has a two-stage structure with a large diameter part (10a) on the upper end side (base end side) and a small diameter part (10b) continuous to the lower end (tip) of the large diameter part (10a). A first stage heat station (1) is formed at the lower end of the large diameter portion (10a) and is maintained at a temperature level of, for example, 55 to 60 degrees Celsius.
1), but the lower end of the small diameter part (10b) is lower than the first stage heat station (11), for example, 15 to 20
A second heat station (12) that is maintained at a temperature level of
The helium gas in the refrigerator is pre-cooled.

A slack piston (15) is disposed inside the upper end of the large diameter portion (10a) of the cylinder (10) and defines an intermediate pressure chamber (13) inside the large diameter portion (10a). 13) is constantly in communication with the surge volume (7) in the valve stem (4) via an orifice (14). The slack piston (15) is approximately cup-shaped with a bottom wall, and the upper end of its inner circumference is connected to the valve stem (15).
4), and the lower end of the outer circumference is in airtight sliding contact with the inner circumference of the large diameter portion (10a) of the cylinder (10). In addition, a center hole (15a) is provided at the center of the bottom wall of the slack piston (15), and a plurality of communication holes (15b) are provided at the corners of the bottom wall to communicate the inside and outside of the piston (15).
, (15b), . . . are formed through each other.

Also, a displacer (16) is installed inside the cylinder (10).
is inserted so that it can reciprocate. This displacer (
16) is continuous with a large diameter part (16a) arranged to be airtightly slidable in the large diameter part (10a) of the cylinder (10), and a lower end (tip) of the large diameter part (16a). (10)
It has a two-stage structure consisting of a small diameter part (10b) and a small diameter part (16b) arranged so as to be airtightly slidable, and a large diameter part (16b).
A sealed space is formed inside each of the small diameter portion (16b) and the displacer (16), and the space inside the cylinder (10) is
) and the gas supply/discharge chamber (17) surrounded by the slack piston (15), and the large diameter part (16) of the displacer (16).
16a) and the large diameter part (10a) of the cylinder (10), a first stage expansion chamber (18) corresponding to the first stage heat station (11), and a small diameter part (16b) of the displacer (16). and the small diameter part (10) of the cylinder (10)
b) surrounded by the second stage heat station (12);
It is divided into a second stage expansion chamber (19) corresponding to the second stage expansion chamber (19).

Further, at the lower end of the large diameter portion (16a) of the displacer (16), there are communication holes (20), (20) that constantly communicate the sealed space inside the large diameter portion (16a) with the first stage expansion chamber (18). It is formed. In addition, communication holes (21), (21) are provided at the upper end of the small diameter portion (16b) to constantly communicate the space inside the small diameter portion (16b) with the first stage expansion chamber (18), and communication holes (21) are provided at the lower end of the small diameter portion (16b) to constantly communicate the space within the small diameter portion (16b) with the first stage expansion chamber (18). A communication hole (2) that constantly communicates with the second stage expansion chamber (19)
2) and (22) are formed, respectively.

Furthermore, the large diameter portion (16a) of the displacer (16)
) A tubular locking piece (23) that communicates the space inside the large diameter portion (16a) with the gas supply/discharge chamber (17) is integrally provided at the upper end, and the locking piece (23) is connected to the slack. Piston (15
) The piston (15) passes through the center hole (15a) of the bottom wall.
A piston (15
) A flange-shaped locking part (23a) that engages with the bottom wall is integrally formed, and when the slack piston (15) moves, the displacer ( 16), that is, the displacer (16) is moved to follow the piston (15) with a delay of a predetermined stroke.

The large diameter portion (16a) of the displacer (16)
) is the first stage regenerator (24) (regenerator), and the small diameter part (16b) is the second stage regenerator (24) (regenerator) in the sealed space.
A stage regenerator (25) is fitted respectively.

These regenerators (24) and (25) are both regenerator type heat exchangers. Specifically, the first stage regenerator (24) has a large number of disc-shaped copper meshes stacked together as a cold storage material in a closed space, while the second stage regenerator (25) A large number of lead balls (lead shots) with a predetermined diameter are filled and sealed in the space as a cold storage material, and the mesh of these meshes and the gaps between the lead balls are used as gas passages, and the cold heat of the helium gas flowing through this gas passage is is stored in the mesh and each lead bulb. That is, the displacer (16) is connected to the cylinder (10
) during the intake stroke, the mesh and lead bulb whose temperature has dropped to a cryogenic level in the previous exhaust stroke are transferred from the gas supply and exhaust chamber (17) to the first and second stage expansion chambers (18), (
19), and the gas is cooled to near cryogenic levels by heat exchange between the two. On the other hand, when the displacer (16) is in the downward exhaust stroke, the mesh and a lead ball, and the mesh and the lead ball are cooled again to near cryogenic levels by heat exchange between the two.

On the other hand, the valve motor assembly (40) has a cylindrical valve housing (40) with a closed bottom and a closed upper end.
1) and a valve stem (42) that airtightly closes the lower end opening of the housing (41). a high pressure gas inlet (43) connected to the discharge side;
A low pressure gas outlet (44) connected to the suction side is opened. Further, a gas supply/discharge port (45) having the same diameter as the gas supply/discharge port (5) of the cylinder assembly (3) is opened at the lower end of the valve stem (42). A valve chamber (46) communicating with the high-pressure gas inlet (43) is formed inside the valve housing (41), and the upper surface of the valve stem (42) faces the valve chamber (46).

The valve stem (42) has a first gas passage (48) whose upper half is branched into two and communicates the valve chamber (46) with the gas supply/discharge port (45), and a first gas flow passage (48) whose upper half is divided into two and which communicates the valve chamber (46) with the gas supply/discharge port (45). 1 gas flow path (48) to the low pressure bow of the valve disc (51), which will be described later.
(53), and the other end communicates with the low pressure gas outlet (44) via a communication path (50) formed in the valve housing (41).
) are formed through it. Both gas channels (48).

(49) is the valve stem (42) as shown in FIG.
) At the upper surface, the valve chamber (46) is located at the center of the valve stem (42) in the second gas flow path (49), and the above-mentioned part is located at the two branched portions of the first gas flow path (48). The openings are respectively symmetrical to the opening of the second gas flow path (49).

Further, a valve disc (51) as a switching valve is disposed in the valve chamber (46) and is rotatably driven by a valve motor (54). ) and a communication path (50) communicating with the low-pressure gas outlet (44) are alternately communicated with the gas supply/discharge port (45).

Specifically, the valve disc (51) is non-rotatably and slidably connected to the output shaft (54a) of the valve motor (54). Further, a spring (55) is installed between the upper surface of the valve disk (51) and the motor (54), and the spring force of this spring (55) and the high pressure helium gas introduced into the valve chamber (46) The pressure causes the lower surface of the valve disc (51) to become attached to the valve stem (42).
It is pressed against the top surface with a constant pressure. Also, the third
As shown in the figure, the lower surface of the valve disc (51) has a pair of high-pressure ports (52), (52), which are formed by cutting a predetermined length toward the center from the radially opposing outer peripheral edges of the valve disc (51).
52) and the high pressure boats (52) are arranged at an angular interval of approximately 90'' in the rotational direction of the valve disc (51) with respect to the high pressure boat (52) (52), and are arranged from the center of the lower surface of the valve disc (51) toward the vicinity of the outer peripheral edge. A low pressure port (53) is formed by cutting out in the diametrical direction.The valve disc (51) is rotated by driving the valve motor (54) while pressing its lower surface against the upper surface of the valve stem (42). When the switching operation is performed, the high pressure gas inlet (43) or the low pressure gas outlet (44) is alternately communicated with the gas supply/discharge port (45) at a predetermined timing according to the switching operation of the valve disc (51). I have to.

Furthermore, as a feature of the present invention, the gas supply/discharge port (5) of the cylinder assembly (3) and the gas supply/discharge port (45) of the valve motor assembly (40) are the gas supply/discharge port (5), ( 45) of a large diameter (e.g. 3/8 inch) first refrigerant pipe (60) having a cross-sectional area equivalent to the first refrigerant pipe (60);
A branch connection is made from the middle of the refrigerant pipe (60), and a second refrigerant pipe (61) having a smaller diameter (for example, 1/4 inch) than the first refrigerant pipe (60) is connected by two pipes.

The first refrigerant pipe (60) is operated by a pair of manually operated first on-off valves (62), (62) and a second refrigerant pipe (60).
The refrigerant pipe (61) has a similar pair of second on-off valves (63),
These opening/closing valves (62) are adapted to be opened and closed by (63), respectively.

(63) constitutes a switching means that selectively switches the communication between both gas supply/discharge ports (5), (45) to the first or second refrigerant pipes (60), (61).

By switching the valve disc (51) in the valve motor assembly (40), the high pressure gas from the high pressure gas inlet (43) or the low pressure gas outlet (44) is connected to the gas supply/discharge port (5) of the cylinder assembly (3). The slab piston (15) and the displacer (16) are made to reciprocate within the cylinder (10) by applying low-pressure gas alternately to the valve disc (51), as shown in Fig. 2(a). the inner ends of the boats (52), (52) are each a first gas flow path (48) on the upper surface of the valve stem (42);
(48), the valve chamber (46) is connected to the high pressure boat (52), (52) and the first gas flow path (48).
) and the refrigerant pipe (60) (or (61)) to the gas supply and discharge chamber (17) in the cylinder (10), the first and second
Stage expansion chamber (18).

(19), each of these chambers (17) to (19)
By introducing high-pressure helium gas into the tank, the slack piston (15) and the displacer (16) driven by the piston (15) are raised. on the other hand,
As shown in FIG. 2(b), the outer end of the low pressure port (53), which is in constant communication at the center with the second gas flow path (49) that opens on the upper surface of the valve stem (42), is connected to the first gas flow path. (48)
When it matches, each chamber (
17) to (19) to refrigerant piping (60) (or (61)
, first gas flow path (48), (48), low pressure port (
53), each chamber (17) is connected to the low pressure gas outlet (44) via the second gas flow path (49) and the communication path (50).
By discharging the helium gas filled in ~ (19) to the low pressure gas outlet (44), the slack piston (
15) and the displacer (16), and as the displacer (16) moves downward, the expansion chamber (18)
, (19) to generate cold in each heat station (11), (12) by expansion of helium gas in the heat station (11), (12).

Next, the operation of the above embodiment will be explained.

During cool-down, the 5QUID is gradually cooled to a low temperature level as the GM refrigerator and JT refrigerator operate.
After the temperature of the 5QUID drops to the cryogenic level (approximately 4K), the refrigerator shifts to a steady operating state, and in that state, the
QUID is activated.

To explain in detail the operation of the above GM refrigerator, first, during cool-down operation, the second on-off valve (63) is manually operated.
, (63) are both opened, and the first on-off valve (62)
, (62) are closed together.

For this reason, the gas supply and exhaust port (
5) and the gas supply/discharge port (45) of the valve motor assembly (40) are communicated through a small diameter second refrigerant pipe (61).

When the pressure inside the cylinder (10) in the cylinder assembly (3) of the expander (2) is low and the slack piston (15) and displacer (16) are at the lower end position, the valve motor assembly (40 ) is driven by the valve motor (54) of the valve disc (51
) rotates, and its high pressure port (52) is rotated, as shown in FIG. 2(a).

(52) is the first gas flow path (
48), matching the valve disc (51) with (48)
) opens to the high pressure side. Along with this, the valve motor assembly (
The high-pressure helium gas at room temperature supplied to the valve chamber (46) of the valve disc (51) is supplied to the high-pressure port (
52), (52) and the first gas flow path (48) to the gas supply/discharge port (45).
5) into the gas supply and discharge chamber (17) below the slack piston (15) via the second refrigerant pipe (61), the gas supply and discharge port (5) of the cylinder assembly (3), and the gas flow path (8). be done. Furthermore, this gas is transferred from the gas supply/discharge chamber (17) to each regenerator (24) of the displacer (16).
, (25) and then each expansion chamber (18), (19
), and this regenerator (24), (2
5), it is cooled by heat exchange with the copper mesh and lead bulbs that have been cooled in the previous exhaust stroke.

In addition, an intermediate pressure chamber (
13) communicates with the surge volume (7) via the orifice (14), so its pressure is maintained at a constant and appropriate value. Therefore, when high pressure helium gas is introduced into the gas supply/discharge chamber (17), the internal pressure becomes higher than that of the intermediate pressure chamber (13), and both chambers (13), (1
7) causes the piston (15) to rise.

When the piston (15) moves up by a predetermined stroke, the bottom wall of the piston (15) engages with the locking piece (23) at the upper end of the displacer (16), and the displacer (16) responds to pressure changes. The displacer (1) is pulled up by the piston (15) with a delay.
6) causes the expansion chambers (18) and (1
9) is further filled with high pressure gas (intake stroke).

After this, the valve disc (51) rotates 90 degrees and closes, but the displacer (16) continues to rise due to inertia, and as a result, the air inside the gas supply and discharge chamber (17) above the displacer (16) rises. Helium gas enters the first and second stage expansion chambers (18).

Move to (19).

Then, after the displacer (16) reaches the rising end position, the valve disc (51) rotates 90'', and as shown in FIG.
As shown in b), the low pressure boat (53) is connected to the first gas flow path (
48), the valve disc (51) opens to the low pressure side, and with this valve opening, the helium gas in each expansion chamber (18), (19) below the displacer (16) undergoes Simon expansion. Cooling occurs due to the expansion of helium gas (expansion stroke).

This extremely low-temperature helium gas passes through the gas supply/discharge chamber (1
7) Return inside, while regenerator (24),
(25) While cooling the copper mesh and lead bulb inside, it is heated to room temperature.

This room temperature helium gas is then stored in the gas supply and exhaust chamber (17
), and contrary to the above, the gas flow path (8), the gas supply/discharge port (5), the second refrigerant pipe (61), the gas supply/discharge port (45) of the valve motor assembly (40), The first gas flow path (48), the low pressure boat (
53) and a low pressure gas outlet (44) via the communication path (50).
) from where it is sucked into the compressor (1). With this gas discharge, the gas pressure in the gas supply/discharge chamber (17) decreases and becomes lower than that in the intermediate pressure chamber (13).
3) The slack piston (15) descends due to the pressure difference at (17), and after the bottom wall of this piston (15) contacts the top surface of the displacer (16), the displacer (16) is pressed. The downward movement of the displacer (16) causes the expansion chambers (18), (19
) is further discharged to the outside of the expander (2) (exhaust stroke).

Next, the valve disc (51) rotates 90 degrees and closes, and after this, the displacer (16) descends to the lower end position, and the gas in the expansion chambers (18) and (19) is exhausted to return to the initial state. return. With the above, one cycle of the operation of the expander (2) is completed, and the same operation as described above is repeated thereafter. By repeating this process, both heat stations (11) and (12) of the cylinder (10) are gradually cooled, and the helium gas in the JT refrigerator that has received the cold from both heat stations (11) and (12) is precooled. , this JT refrigerator cools the 5QUID to a cryogenic level.

During this cool-down operation, the temperature at the low-temperature end of the cylinder (10) is high, so the influence of compression heat retention on the normal-temperature end is greater than after the cool-down, but at this time, the cylinder assembly (3) and valve motor assembly (40)
The gas supply/discharge ports (5) (45) communicate with each other through the small-diameter second refrigerant pipe (61), so the amount of refrigerant gas flowing back and forth through this small-diameter refrigerant pipe (61) increases, and the cylinder (10) The heat of compression taken away at the low temperature end is effectively radiated by heat exchange with the refrigerant gas. For this reason, the expander (2
) is separated into a cylinder assembly (3) and a valve motor assembly (40).
) The temperature rise at the normal temperature end can be effectively suppressed, and the intermediate pressure by the surge volume (7) can be maintained within an appropriate range, thereby maintaining normal reciprocating motion of the displacer (16) and shortening the cool-down time of the refrigerator. Can be maintained on time.

Then, after a predetermined time has elapsed since the start of the refrigerator, or after the temperature of the SQU ID has decreased to a predetermined temperature, the cool-down operation ends and the refrigerator enters a steady operating state. In this state, the second on-off valve (63), (
63) is closed, and instead the first on-off valve (62),
(62) is opened, and the gas supply/discharge port (5) of the cylinder assembly (3) and the gas supply/discharge port (45) of the valve motor assembly (40) are communicated through the large diameter first refrigerant pipe (60). Ru. The rest is the same as in the cool-down operation described above.

In this steady operating state, each gas supply/discharge port (
5) and (45) communicate with each other through the large-diameter first refrigerant pipe (60), the pressure loss of the gas in this large-diameter refrigerant pipe (60) is reduced, and the Pv indicated area of the refrigerator is reduced. is kept large, and thus its refrigeration capacity can be maintained at an increased level.

Therefore, in this embodiment, the expander (2) is composed of a valve motor assembly (40) and a cylinder assembly (3) that are separated from each other, and the valve motor (
54) is separated from the lower end of the cylinder (10),
The magnetic flux from the valve motor (54) is suppressed from adversely affecting the magnetic flux detection of the 5QUID as noise, and therefore the 5QUID can be cooled by the refrigerator without any problem.

(Other Embodiments) FIG. 4 shows a second embodiment. Note that the same parts as in FIG. 1 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

In this embodiment, the gas supply/discharge ports (5) and (45) of the cylinder assembly (3) and valve motor assembly (40) of the expander (2') are connected to two parallel first and They are connected by the second refrigerant pipes (65) and (66), and the total cross-sectional area of both open pipes (65) and (66) is approximately the cross-sectional area of the gas supply and discharge port (5) (or (45)). considered to be the same.

The first refrigerant pipe (65) has a pair of manually operated on-off valves (67) as switching means for opening and closing the pipe (65).
67) is provided, and these double on-off valves (67), (6
7) By opening and closing both gas supply and discharge ports (5), (45)
The cross-sectional area of the passage when communicating with the two refrigerant pipes (65),
(66), and a second mode in which the passage cross-sectional area is smaller than the passage cross-sectional area in the large area mode.
It is possible to switch between the small cross-sectional area mode and the small cross-sectional area mode in which only the refrigerant pipe (66) is selected.

Therefore, in this embodiment, during cool-down operation of the refrigerator, the on-off valves (67), (67) are closed, and the cylinder assembly (3) and valve motor assembly (4) are closed.
Both gas supply and discharge ports (5) (45) with 0) communicate with each other only through the second refrigerant pipe (66), and both gas supply and discharge ports (5),
(45) The cross-sectional area of the passage when communicating becomes smaller. Therefore, the amount of gas flowing back and forth in the refrigerant pipe (65) increases, and the accumulation of compression heat at the normal temperature end of the cylinder (10) is suppressed, thereby maintaining the reciprocating motion of the displacer (16) appropriately and cooling down. It can save time.

On the other hand, during steady operation after cool-down, the on-off valves (67) and (67) are opened, and both gas supply and discharge ports (5) are opened.
), (45) are two refrigerant pipes (65).

(66). As a result, refrigerant piping (65
), (66) can be reduced to maintain a large refrigerating capacity of the refrigerator.

In the second embodiment described above, the number of refrigerant pipes having the same diameter may be increased to three or more, and the communication cross-sectional area of both gas supply and discharge ports (5) and (45) can be changed by opening and closing the on-off valve. 2
You may switch it so that it is the same.

In addition, the multiple refrigerant pipes connecting both gas supply and discharge ports (5) and (45) do not necessarily have to have the same diameter, and both gas supply and discharge ports (5) and (45) are connected to each other with different diameters. They may be connected by multiple refrigerant pipes, and by selecting them, they can be combined so that the passage cross-sectional area is different between the large cross-sectional area mode and the small cross-sectional area mode, and the passage cross-sectional area in both modes is different. The area ratio can be varied as necessary.

Further, although each of the above embodiments is an example of cooling a 5QUID, the present invention can also be applied to the case of cooling a superconducting device in which magnetic flux from a motor is harmful.

(Effects of the Invention) As explained above, in the invention of claim (1), in a gas pressure driven GM refrigerator, the expander is separated into a valve motor assembly and a cylinder assembly, and the gas of both assemblies is The gas supply and discharge ports are connected with two types of parallel refrigerant pipes with different diameters, and communication between both gas supply and discharge ports is switched.

Further, in the invention of claim (2), the gas supply and discharge ports of both assemblies are connected to each other by a plurality of parallel refrigerant pipes, and the cross-sectional area modes of the refrigerant pipes that communicate between the two gas supply and discharge ports are divided into two types, large and small. The selection can be changed so that Therefore, according to these inventions, in a cool-down operation where the accumulation of compression heat at the cold end of the cylinder has a large effect, the cross-sectional area of the refrigerant piping can be reduced, and the compression heat taken away at the cold end of the cylinder can be reduced. This effectively suppresses the temperature rise at the normal temperature end of the cylinder and maintains the intermediate pressure within an appropriate range, allowing normal reciprocating motion of the displacer. By making it small, the PV indicated area of the refrigerator can be kept large. Therefore, even if the expander is a gas pressure-driven GM refrigerator in which the expander is separated into a cylinder assembly and a valve motor assembly in order to reduce magnetic noise for 5QUID etc., the cool-down operation time can be maintained shortened and the cool-down operation can be continued after the cool-down operation. It is possible to increase and maintain the refrigerating capacity of

[Brief explanation of the drawing]

1 to 3 show a first embodiment of the present invention, FIG. 1 is a sectional view of the expander, FIG. 2 is a plan view of the upper surface of the valve stem facing the valve chamber, and FIG. 3 is the lower surface of the valve disk. FIG. FIG. 4 is a diagram corresponding to FIG. 1 showing the second embodiment. Figure 5 is a Pv diagram for integrated and separate expanders, Figure 6
The figure is a characteristic diagram showing the relationship between the pipe diameter and pipe length of the refrigerant pipe and the Pv area ratio, and Figure 7 is a characteristic diagram showing the relationship between the pipe diameter and pipe length of the refrigerant pipe and the temperature at the normal temperature end of the cylinder. . (1)... Compressor (2), (2')... Expander (3)... Cylinder assembly (4)... Valve stem (closure member) (5)... Gas supply and exhaust Port (7)...Surge volume (10)...Cylinder (11), (12)...Heat station (13)
... Intermediate pressure chamber (15) ... Slack piston (16) ... Displacer (17) ... Gas supply and discharge chamber (18), (19) ... Expansion chamber (24), (25) ... Regenerator (40)
... Valve motor assembly (42) ... Valve stem (43) ... High pressure gas inlet (44) ... Low pressure gas outlet (45) ... Gas supply and discharge port (51) ... Valve disc (Valve) (54)...
・Valve motor (60)...First refrigerant pipe (61)...Second refrigerant pipe (62), (63)...Opening/closing valve (switching means) (65)
, (66)...Refrigerant piping...Opening/closing valve (switching means) (5)...Gas supply/discharge port (7)...Surge volume...Displacer (42)...Valve stem (43)... )...High pressure gas inlet (44)...Low pressure gas outlet...Valve motor...Opening/closing valve (switching means) Figure 3 Figure 2 (a) Section 2 (b)

Claims (2)

[Claims] (1) A compressor (1) that compresses refrigerant gas to generate high-pressure gas, and an expander (1) that adiabatically expands the high-pressure gas supplied from the compressor (1) to generate cryogenic cold.
2), wherein the expander (2) supplies and discharges gas into the cylinder (10) through the gas supply and discharge port (5) to generate a displacer (16).
an expansion chamber (18) within the cylinder (10);
The cylinder assembly (3) expands the gas at (19).
) and a switching valve (51) by a valve motor (54).
a valve motor that switches communication between a high pressure gas inlet (43) and a low pressure gas outlet (44) connected to the discharge side and suction side of the compressor (1), respectively, and the gas supply/discharge port (45) by driving the compressor (1); The gas supply/discharge port (5) of the cylinder assembly (3) and the gas supply/discharge port (45) of the valve motor assembly (40) are separated from the assembly (40).
) means the first refrigerant pipe (60) and the first refrigerant pipe (60).
) is connected in parallel with a second refrigerant pipe (61) having a smaller diameter than the first refrigerant pipe (60), and communicates with the first or second refrigerant pipe (61) to connect both gas supply/discharge ports (5), (45). Refrigerant piping (6
switching means (62) for selectively switching between 0) and (61);
, (63). (2) A compressor (1) that compresses refrigerant gas to generate high-pressure gas, and an expander (1) that adiabatically expands the high-pressure gas supplied from the compressor (1) to generate cryogenic cold.
2), wherein the expander (2) supplies and discharges gas into the cylinder (10) through the gas supply and discharge port (5) to generate a displacer (16).
an expansion chamber (18) within the cylinder (10);
The cylinder assembly (3) expands the gas at (19).
) and a switching valve (51) by a valve motor (54).
a valve motor that switches communication between a high pressure gas inlet (43) and a low pressure gas outlet (44) connected to the discharge side and suction side of the compressor (1), respectively, and the gas supply/discharge port (45) by driving the compressor (1); The gas supply/discharge port (5) of the cylinder assembly (3) and the gas supply/discharge port (45) of the valve motor assembly (40) are separated from the assembly (40).
) are connected by multiple refrigerant pipes (65), (66), and the cross-sectional area of the passage when both gas supply/discharge ports (5), (45) are in communication is determined by at least two or more refrigerant pipes (65), Switching means (67) for switching between a large cross-sectional area mode by selecting (66) and a small cross-sectional area mode by selecting a refrigerant pipe whose cross-sectional area is smaller than the passage cross-sectional area in the large cross-sectional area mode.
) A cryogenic refrigerator characterized by being provided with.